1. Field of the Invention
The present invention relates to an overlapped transfer-preventing mechanism provided in an image-forming apparatus and the like for preventing papers from being overlappedly transferred.
2. Description of the Prior Art
In an image-forming apparatus, papers for fixing an image formed are required and a plurality of said papers are usually piled on a cassette plate, which is detachably provided in said image-forming apparatus, in layers to be drawn out one by one by means of a paper-supplying roller.
In order to draw out the papers by means of said paper-supplying roller, it is necessary that the papers are pressed against the paper-supplying roller arranged thereabove at a front end portion thereof to apply a paper-supplying pressure to the papers. To this end, said cassette plate is risen on the paper-supplying roller at a front end thereof by means of an actuator such as a spring force or a motor and a cylinder device.
The papers drawn out by means of the paper-supplying roller are treated with a separating roll, which is arranged in the vicinity of the paper-supplying roller, to prevent an overlapped transfer thereof. Said separating roll comprises an upper separating roll, which is rotatably driven in the same manner together with the paper-supplying roller to be brought into contact with an upper surface of the papers, and a lower separating roll, which is brought into contact with a lower surface of the papers but not rotated in a paper-supplying direction, to prevent the papers from being overlappedly transferred by a difference between frictional resistances which the papers receive from both rolls. In short, said upper surface of the paper-supplying roller hardly receives said frictional resistance from the upper separating roll, which is rotatably driven in the same direction together with the paper-supplying roller, but said lower surface of the papers receives a comparatively large frictional resistance from the lower separating roll, which is not rotated in said paper-supplying direction, and thus, when two pieces or more of paper are transferred at the same time, a supply of lower paper is stopped by said difference between the frictional resistances.
With the above described separating roll, if the lower separating roll is brought into sliding contact with the lower surface of the papers always at the same position, it is biasedly worn, so that a surface-changing mechanism for rotating the lower separating roll by one rotation severalth by the use of an actuator, such as solenoid, after counting an appointed time is provided.
However, in the case where said actuator, such as solenoid, is used, problems have occurred in that not only the construction is complicated and the cost is increased but also the layout is reduced in degree of freedom.
In addition, in case of the manual paper-supply, it has been required to regulate an interval between the upper separating roll and the lower separating roll depending upon a kind of the papers. For example, in the case where the thick papers, such as OHP, are supplied, the lower separating roll is regulated so as to be lowered in height in order to increase said interval. Also in the case where the lower separating roll is regulated so as to be adjustable in height, it has been desired to provide said surface-changing mechanism simple in construction.
However, in the case where the large interval is set between both separating rolls, as above described, the papers enter too deeply to be engaged with a regist switch, whereby making a jam-display, according to circumstances, when the papers are set. Accordingly, it has been desired also that such the disadvantage is prevented from occurring.
However, in order to surely prevent the overlapped transfer and accurately supply the papers, as above described, the appointed interval must be set between the upper separating roll and the lower separating roll. However, both separating rolls are usually arranged at positions where they are not brought into contact with each other, so that the operation for regulating the interval between both separating rolls has been troublesome and took time. Accordingly, it has been desired not only in its manufacturing step but also in its aftercare step that such the disadvantage is solved.